A police officer who intervened to stop a shooting spree at America's biggest military base was hailed today a heroine as she received treatment for the wounds received in a shoot-out with the gunman.

Major Nidal Hasan, an army psychiatrist due to be posted to Afghanistan, shot dead 13 people and wounded 30 others after opening fire with two handguns at Fort Hood yesterday afternoon.

But the death toll from the rampage could have been far worse had it not been for the actions of Sergeant Kimberly Munley, a civilian police officer stationed at the base who was the first on the scene as Major Hasan picked off his victims.

Sergeant Munley managed to hit Major Hasan four times but was herself hit by a bullet that passed through both her legs, according to witnesses.

Colonel John Rossi, briefing reporters at Fort Hood this morning, said that Major Hasan's victims, who were killed in a part of the base used to process soldiers for deployment to Iraq and Afghanistan, had all been unarmed. Sergeant Munley had been the first armed person on the scene and had immediately taken him on.

"Her efforts were superb," he said.

The base commander, Lieutenant-General Bob Cone, also paid tribute: “She happened to encounter the gunman. In an exchange of gunfire, she was wounded but managed to wound him four times,” he said.

“It was an amazing and aggressive performance by this police officer.”

Colonel Steven Braverman, commander of the base hospital and Major Hasan's supervisor, said that Sergeant Munley was in a stable condition in a nearby community hospital.

She is likely to return home to a hero's welcome, although her Twitter page – which features a picture of her with the country music star Dierks Bentley at the Fort Hood "Freedom Fest" on July 4 – suggests she is not the type to have her head turned.

Her Twitter biography reads: "I live a good life ... a hard one, but I go to sleep peacefully @ night knowing that I may have made a difference in someone's life."

It emerged today that Major Hasan, a Muslim who had argued with his comrades against the wars in Iraq and Afghanistan and had been trying to get out of the Army, shouted "Allahu akbar" – Arabic for "God is great" – as he launched the attack.

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